Nick Momrik, Technical Assistant at Automattic, announced a new feature at WordPress.com that will email any post changes that are made after a post is published.
Nick describes the new functionality:
Today we’re launching a feature called Email Post Changes to help blogs with multiple authors collaborate better on the same posts and pages. If you turn it on, we’ll instantly notify you by email whenever a change is made to a post on your site.
Email Post Changes is also available as a Plugin, for self-hosted WordPress users, in the WordPress Plugin directory.